1. Field of the Invention
The present invention relates to exercise devices used on the human body and, more particularly, to exercise devices wherein the resistance curve experienced by the human body can be selectively and easily adjusted.
2. Background of the Invention
As discussed in some detail in U.S. Pat. No. 5,286,243, most exercise devices provide only a single resistance curve that cannot be altered to conform to individual requirements. A number of exercise devices enables resistance curves to be varied, but only with severe practical and functional limitations.
In the exercise device of U.S. Pat. No. 2,855,199, for example, the resistance can be varied through the range of motion of an exercise by selectively adjusting the radial position of a weight arm upon which a weight member is affixed. Through the relative placement of the weight arm with respect to the exercise arm, different resistance curves can be experienced during the course of the exercise motion. That device, however, has inherent limitations that make its practical application severely limited. Moreover, those limitations can be dangerous in an uncontrolled setting.
For example, because the degree of rotation of the weight arm is equivalent to that of the exercise or leg arm of that device, the sinusoidal resistance force generated by the weight arm is directly correlated to (that is, having a one-to-one correlation with) the degree of rotation of the exercise arm. Such direct correlation results in several substantial limitations. Seldom if ever is a desired sinusoidal resistance curve achieved through a direct correlation between the rotation of the exercise arm and the rotation of the weight arm, especially in a situation where the radial position of the weight arm is being varied. To illustrate, if the weight arm is set to place maximum overload at the beginning of the motion, and the exercise arm is rotated more than 90 degrees, the weight arm will generate negative resistance during the end of the exercise motion. A resistance force that suddenly changes from a positive resistance force to a negative resistance force may cause the user to lose control of the exercise arm, resulting in a substantial risk of injury. Moreover, when negative resistance occurs in the device of U.S. Pat. No. 2,855,199, the user must cease the exercise until the exercise arm is brought back to the starting position. Additionally, a negative resistance force is clearly undesirable for strength conditioning. Finally, a resistance curve that either decreases or increases too rapidly, whether or not it results in a negative resistance force, leads to an awkward exercise motion and less than optimal training.
The device of U.S. Pat. No. 2,855,199 is further limited by providing only a single sinusoidal resistance force via a single weight arm thereof. Even absent the concerns of negative resistance, an excessive, or a too rapidly changing resistance, less than optimal control over the resistance forces results from the single sinusoidal pattern. Often, the desired resistance curve for a particular exercise motion for a specific individual is something other than a simple sinusoidal resistance curve. It is, therefore, highly desirable to enable manipulation of the rate of change of the pattern of the resistance curve. Such manipulation is impossible with a single weight arm.
Furthermore, because the variance of the force is achieved by altering the radial position of the weight in the device of U.S. Pat. No. 2,855,199, to alter the resistance force the user must either unload the weight arm and then rotate it or attempt to rotate the loaded weight arm. In the former case, the user is substantially inconvenienced. In the latter case, the user is risking serious injury. Additionally, a linkage for connecting a weight arm at different radial positions is quite expensive and generally leads to a loose connection point.
U.S. Pat. No. 4,405,128 disclosed an exercise device comprising multiple torque arms designed to enhance or offset the weight of the human body as an individual performs a sit-up exercise. Through offsetting body weight, the invention is intended, in part, to assist weak persons in performing sit-ups. The invention thus has the inherent requirement of generating negative resistance forces to counterbalance the user""s body weight. Additionally, the degree of rotation of the torque arms and the degree of rotation of the chest engaging means are required to correlate on a one-to-one basis. Otherwise the desired counter-balancing would not be achieved. While such operation may be desirable for a sit-up device seeking to counter-balance and add resistance to the body-weight of the user, the negative resistance generated by the torque arms and the direct correlation between the rotation of the torque arms and that of the chest engaging means results in the same inherent limitations discussed above in connection with U.S. Pat. No. 2,855,199.
Very recently, a number of advances have been made in the exercise arts. U.S. Pat. No. 5,286,243, for example, discloses an exercise device combining the resistance generated by a plurality of torque arms with a conversion mechanism that creates a greater degree of rotation of the torque arms than that of the exercise arm. It is possible, through proper relative placement of weights along designated torque arms, to achieve desirable resistance curves. However, both positive and negative resistance forces are achievable during the exercise motion. Consistently maintaining a desired resistance curve and consistently maintaining a positive resistance load throughout the exercise motion requires proper adjustment of numerous torque arm variables. The proper adjustment of such variables may in many cases be beyond the patience and/or the knowledge of the average exercise equipment user.
It is desirable to develop an exercise device that overcomes the limitations of current exercise devices. It is particularly desirable to develop an exercise device that provides a plurality of resistance curves, but will not result in a resistance curve that changes too rapidly or results in a negative resistance force.
The present invention provides an exercise device in which resistance curves can be selectively varied and controlled to achieve a desired positive resistance curve notwithstanding the degree of rotation of the exercise motion. The present invention utilizes a unique torque arm assembly that preferably comprises a plurality of torque arms positioned at different radial positions such that the relevant placement of weight members on the torque arms results in an endless array of resistance curves. In any such resistance curve, the present invention continuously maintains a positive resistance force regardless of the manner of loading of the torque arms.
Generally, the exercise device of the present invention comprises a support frame upon which a first shaft is rotatably supported. A user interface member (or exercise member) is connected to the first shaft such that when the user interface member is displaced by a user the first shaft is caused to rotate. A second shaft is also rotatably supported on the support frame. A torque arm assembly comprising of a plurality of torque arms is connected to the second shaft. Each of the plurality of torque arms is adapted to support a weight member thereon. In one embodiment, an independent weight member on each of the plurality of torque arms is linearly positionable on each of the plurality of torque arms. A conversion mechanism connects the first and the second shafts to control the degree of rotation of the second shaft in such a manner that the resistance generated by the torque arm assembly cannot result in a negative resistance force. In preventing a negative resistance force, the conversion mechanism may either limit or magnify the rotation of the second shaft, provided that in no case is the rotation of the second shaft sufficient to create a negative resistance force.
The support frame is preferably free standing and preferably comprises interconnected vertical and horizontal frame work members. The conversion mechanism preferably comprises a beltwheel assembly. The beltwheel assembly preferably comprises a first beltwheel attached to the first shaft and a second beltwheel attached to the second shaft. The rotation of the first beltwheel and the second beltwheel is correlated via a belt. One end of the belt is connected to the second beltwheel. The belt is then wrapped around a portion of the first beltwheel and connected at its other end to the second beltwheel. Preferably, a connector pinches the belt to the first beltwheel such that the rotation of the first beltwheel causes the rotation of the second beltwheel without having the belt slip. A conversion mechanism is thereby achieved between the first and second shafts in which the degree of conversion (that is, the change in the degree of rotation) is a function of the relative sizes (diameters) of the first and second beltwheels. A similar conversion can be achieved through other means. For example, differently sized rotating members can be used in the form of meshing spur gears or in the form of a gear-and-chain assembly. However, such other conversion mechanisms generally do not provide as smooth an exercise motion as a beltwheel assembly and/or generally increase costs.
The size ratio between the first and second beltwheels is preferably selected so that the maximum degree of rotation applied to the first shaft by the exercise motion of the user is converted to no more than approximately 90 degrees of rotation on the second shaft. More preferably, the maximum degree of rotation applied to the first shaft is converted to no more than approximately 70 degrees of rotation of the second shaft.
A fastening means is preferably provided for attaching the torque arm assembly to the second shaft. Preferably, as illustrated in FIGS. 1 through 6, the torque arms extend radially from a common center. Preferably, the angle between the outermost torque arms is no more than 90 degrees. Preferably, the torque arm assembly comprises three torque arms wherein the angle between each torque arm is approximately 35 degrees. In that embodiment the angle between the outermost torque arms is approximately 70 degrees.
The torque arm assembly is preferably positioned such that the upper torque arm applies a maximum resistance force to the second shaft (and consequently to the first shaft) when the exercise member is in its initial or starting position. Thus, the upper torque arm is preferably located at either the 3 o""clock position or the 9 o""clock position depending upon the direction of rotation. Since the conversion mechanism preferably assures that the second shaft will rotate no more than 90 degrees (and, more preferably, no more than 70 degrees), the torque assembly will never generate a negative resistance force regardless of the manner of the loading of the torque arms by the user.
A means for securing at least one weight member is affixed to each torque arm. In its simplest form, this weight securing means comprises a peg upon which weight plates can be held. It is also possible to have weight members slide along the torque arms to selected positions to create an adjustable resistance force that does not require the removal of the weight members.
In the operation of the present invention, each weight member supported on a torque arm provides a resistance force that follows a sinusoidal curve. If a single torque arm is loaded, the force generated will follow the sinusoidal curve associated with that torque arm. Should more than one torque arm be loaded, the force generated will follow the vector summation of the sinusoidal curves associated with each of the torque arms that are loaded. Thus, the torque assembly permits the user to vary the overall resistance force depending upon the relative placement of weight members on the torque arms.
As discussed above, the conversion mechanism assures that the torque assembly attached to the second shaft rotates the proper degree of rotation regardless of the degree of rotation of the exercise member attached to the first shaft. To determine an appropriate ratio between the first and second beltwheels for any given exercise unit and its associated exercise motion, the degree of rotation of the exercise motion is determined and the ratio between the first and second beltwheels is set accordingly.
For example, assuming that the average exercise motion is 140 degrees, placing a 6-inch beltwheel on the first shaft and a 12-inch beltwheel on the second shaft will result in a desirable 70 degrees of rotation of the second shaft. Further assuming that a counter-clockwise rotation of the second shaft occurs when the first shaft is rotated during the course of the exercise motion, the starting position of the torque assembly is preferably located such that the upper torque arm is located at approximately 3 o""clock (that is, horizontally). In a preferred embodiment, the second torque arm is approximately 35 degrees toward 6 o""clock from the first torque arm, and the third torque arm is approximately 35 degrees toward 6 o""clock from the second torque arm. The positioning of the torque arm assembly in this manner, together with the 2:1 ratio between the first and second shafts, assures that the user will always experience a positive resistance force during the course of the exercise motion, regardless of the manner in which the torque arms are loaded.
By varying the relative loading of the torque arms, an indefinite number of resistance curves can be achieved. The use of a plurality of torque arms is thus a substantial improvement over the case of a single torque arm in which only a single sinusoidal resistance curve is attainable. To illustrate, and using the above-described example of a torque assembly of the present invention comprising three torque arms, assuming the user desires to overload the beginning of the exercise motion, the user loads the upper torque arm (that is, the torque arm at the 3 o""clock position). This loading results in the user experiencing 100% of the resistance at the beginning of the motion and approximately 34% at the end of the motion. If the user wants to overload the middle of the motion, the user loads the middle torque arm. This loading results in the user experiencing 82% of the resistance at the beginning of the motion, 100% of the resistance in the middle of the motion and 82% at the end of the motion. To overload the end of the motion the user loads the lower torque arm. This loading results in the user experiencing 34% of the resistance at the beginning of the motion and 100% of the resistance at the end of the motion. FIGS. 2a through 2c show the beginning, middle and end positions of the three torque arms during the course of an exercise motion assuming that the torque arms have been converted to rotate 70 degrees during the course of the exercise motion.
By loading more than one arm, for example the upper torque arm and the middle torque arm, the user will experience the vector sum effect of the sinusoidal curves generated by the upper and middle torque arms. Thus, the user will experience maximum resistance somewhere between the beginning and the middle of the motion, depending upon the relative ratios of the weights on the two torque arms. A middle to end overload would occur if the middle and lower torque arms were each loaded.
The present invention thus provides incredible variability while never allowing the user to experience the risks associated with negative loading. The combination of the conversion mechanism of the present invention with a properly positioned torque assembly having multiple torque arms conveniently, simply and safely enables satisfaction of the resistance pattern needs of any user.
Other details, objects and advantages of the present invention will become apparent as the following detailed description of preferred embodiments of practicing the invention proceeds.